Fuel efficiency of engines can be an important consideration selection and operation of the engines. For example, fuel efficiency of gas turbine engines in aircraft can be an important (and limiting) factor on how far the aircraft can travel. Some aircraft propulsion systems can include fuel cells in addition to the gas turbine engines. These fuel cells are located upstream of combustors and downstream from compressors of the gas turbine engines. Compressed air that is output by the compressors flows along the length of the engine and into the fuel cells. Part of this air is consumed by the fuel cells in generating electric energy. The rest of the air can flow through or around the fuel cells and into a combustor. This air is then mixed with fuel and combusted in a combustor of the engine.
One problem with known fuel cell-combustor combinations is the requirement of conduits to direct the flow of air into the fuel cells and out of the fuel cells into the combustor. These conduits can increase the size of the fuel cell and engine combination, as well as require heating elements to ensure that the air is sufficiently hot for consumption within the fuel cells.